hadoop-pig-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Daniel Dai (JIRA)" <j...@apache.org>
Subject [jira] Updated: (PIG-1038) Optimize nested distinct/sort to use secondary key
Date Thu, 12 Nov 2009 03:12:39 GMT

     [ https://issues.apache.org/jira/browse/PIG-1038?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Daniel Dai updated PIG-1038:
----------------------------

    Status: Open  (was: Patch Available)

> Optimize nested distinct/sort to use secondary key
> --------------------------------------------------
>
>                 Key: PIG-1038
>                 URL: https://issues.apache.org/jira/browse/PIG-1038
>             Project: Pig
>          Issue Type: Improvement
>          Components: impl
>    Affects Versions: 0.4.0
>            Reporter: Olga Natkovich
>            Assignee: Daniel Dai
>             Fix For: 0.6.0
>
>         Attachments: PIG-1038-1.patch, PIG-1038-2.patch, PIG-1038-3.patch, PIG-1038-4.patch,
PIG-1038-5.patch
>
>
> If nested foreach plan contains sort/distinct, it is possible to use hadoop secondary
sort instead of SortedDataBag and DistinctDataBag to optimize the query. 
> Eg1:
> A = load 'mydata';
> B = group A by $0;
> C = foreach B {
>     D = order A by $1;
>     generate group, D;
> }
> store C into 'myresult';
> We can specify a secondary sort on A.$1, and drop "order A by $1".
> Eg2:
> A = load 'mydata';
> B = group A by $0;
> C = foreach B {
>     D = A.$1;
>     E = distinct D;
>     generate group, E;
> }
> store C into 'myresult';
> We can specify a secondary sort key on A.$1, and simplify "D=A.$1; E=distinct D" to a
special version of distinct, which does not do the sorting.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


Mime
View raw message